On vehicles with a manual transmission, worn shift bushings can cause the transmission to pop out of gear, especially when coasting down in 1st or 2nd gear. Replacing all the shift linkage bushings is pretty straight forward and not expensive and will commonly correct this concern.
Car Problem Reports
Toyota Tercel Worn Shift Bushings Will Cause Manual Transmission to Pop Out of Gear
Toyota Tercel Problem
Drive Train Affected: Manual Transmission
Visitor, 1992 Toyota Tercel, Manual Transmission, 154,000 mi
Pops out of gear in 3rd and 4th gear when cruising, will try to find replacement bushings.